South Korea had proposed Japan use the expression "forced" in the museum exhibits on an old Japanese mine complex linked to its wartime forced labor of Koreans prior to its UNESCO inscription, but Tokyo refused, the foreign ministry said Tuesday.

The ministry had made the call during the negotiations with Japan on the Sado gold and silver mines as a precondition for Seoul's consent to the site's listing as a UNESCO World Heritage, its response submitted to Rep. Lee Jae-jung of the main opposition Democratic Party showed.

"During the negotiation process, we requested the inclusion of historical documents and exhibit texts to contain the term 'forced,' but Japan ultimately did not agree to this request," the ministry said in the document.

The government has come under criticism after the exhibits at the history museum near the Sado mine site turned out to have no description about how thousands of Koreans were taken against their will to toil at the mines during World War II, when Korea was under Japan's colonial rule.

Featuring exhibits at the museum was part of the agreement reached between the two sides before the mine complex won World Heritage status in late July.

Seoul officials have said the government agreed to the inscription as Japan installed the exhibits in advance and promised to carry out its commitments to better reflect the "full" history, as pledged in 2015 when Hashima Island, another forced labor site, was listed on the UNESCO World Heritage list.

But critics have blamed the foreign ministry for not having done enough to ensure Japan properly showed the coercive nature of the forced labor at the Sado mines.

Despite the growing criticism, the foreign ministry had maintained its decision not to reveal the details of the negotiations with Japan and declined to comment whether it specifically asked Japan to use the term "forced" in the exhibits.

The ministry's response Tuesday confirmed that it did.

Earlier in the day, National Assembly Speaker Woo Won-shik issued a statement calling for the foreign ministry to disclose the details of the negotiations on the Sado mines, blaming the government for making a "very wrong" decision.

"We will carefully review the statement and explain to the Assembly over the matter going forward," foreign ministry spokesperson Lee Jae-woong said in a press briefing, without elaborating. (Yonhap)